Conventional microspeakers did not use wideband sound sources due to the limitations of communication technology. However, with the advancement of information and communication technology, the bandwidth of a sound source to be reproduced by a speaker has become wider and the required output has increased. Thus, a conventional microspeaker structure has its limitations in terms of features and reliability.
FIG. 1 is a sectional view showing a conventional sound transducer.
As shown, a typical sound transducer (speaker) includes a frame 1, a yoke 2 inserted and mounted inside the frame 1, an inner ring magnet 3 and an outer ring magnet 4 for transmitting a magnetic flux to the yoke 2 or receiving the magnetic flux from the yoke 2, an inner ring top plate 5 and an outer ring top plate 6 for receiving the magnetic flux from the inner ring magnet 3 or the outer ring magnet 4 and transmitting the magnetic flux to a voice coil 7 at a right angle, the voice coil 7 partially inserted into air gaps between the inner ring magnet 3 and inner ring top plate 5 and the outer ring magnet 4 and outer ring top plate 6, a diaphragm 8, into which the voice coil 7 is attached, for generating a vibration by the up-down movement of the voice coil 7, and a protector 10 having a sound-emitting hole 11 and protecting the diaphragm 8.
The lead-out wire of the voice coil 7 is fixedly adhered to the bottom face of the diaphragm 8 by a wire bond, taken out through the side face of the frame 1 or a groove (not shown) formed at the frame 1, and soldered to a terminal 14 along the outer side face of the frame 1, respectively.
However, this structure has limitations in reproducing wideband sound sources. When it comes to a single film type diaphragm, if a film with low rigidity is used or the diaphragm is thinned, in order to improve low frequency performance, this generates dips in sound pressure at mid-to-high frequencies and particular lateral vibrations at low frequencies, thus causing an increase in defect rate. On the other hand, if the diaphragm is thickened or a film with high rigidity is used, this degrades low frequency performance and results in poor sound balance. For this reason, a film structure for a wideband speaker was conventionally proposed, in which an edge portion and a central portion are made of different film materials.
However, this structure also produces severe lateral vibrations at high-output mode, and can even cause coil breakage, which may lead to serious problems in terms of reliability. Accordingly, a structure using a damper was conventionally proposed to solve these problems.
The components and shape of this damper greatly affect the features and reliability of a microspeaker when configuring the damper. A wrongly-configured damper could be more subject to wire breakage than a voice coil lead-out structure and cause difficulties in correcting lateral vibrations at a particular mode.